A faster way to characterize by triple-quantum-filtered 17O NMR water molecules strongly bound to macromolecules in solution

The simultaneous use of transverse and longitudinal relaxation rates, together with a transverse triple-quantum-filtering NMR sequence, was estimated for the adequate characterization of O-17-water relaxation behavior in protein solutions. A complementary contribution to transverse relaxation was found, which was interpreted as chemical exchange of O-17-water between different sites of the proteins. This contribution was estimated via calibration measurements. Then, for other similar samples, faster experiments could be performed. The analysis of the results obtained in this way gave adequate values of the relaxation rate of water in fast motion, of the fraction of water in slow motion, and of its correlation time. Hence, it permitted the complete characterization of the sample in a reasonable experimental time. (C) 2001 Academic Press.